A conventional receiver is described with reference to FIG. 5. In FIG. 5, conventional receiver 1 has first receiving unit 2 and second receiving unit 3 for diversity-receiving a signal of a radio frequency from the outside. First receiving unit 2 and second receiving unit 3 have first mixer 4 and second mixer 5 for converting the signal of the radio frequency from the outside into an intermediate frequency (IF) signal of an intermediate frequency by one of an upper local method and a lower local method, respectively. First receiving unit 2 and second receiving unit 3 also have first filter 6 and second filter 7 connected to the output side of first mixer 4 and the output side of second mixer 5, respectively.
An example of the conventional art document information related to the invention of this application is Patent document 1.
In conventional receiver 1, the frequency of a local signal supplied to first mixer 4 is substantially equal to the frequency of a local signal supplied to second mixer 5, and the difference between these frequencies is very small. When the local signal to be supplied to first mixer 4 and the local signal to be supplied to second mixer 5 accidentally come as noise into second mixer 5 and first mixer 4, respectively, beat noise occurs in second mixer 5 and first mixer 4. The beat noise occurs at an extremely low frequency and the noise frequency gets close to an intermediate frequency, so that the noise is difficult to be removed by first filter 6 or second filter 7 and the receiving performance of receiver 1 degrades.
[Patent document 1] Japanese Patent Unexamined Publication No. 2005-130279